1. Field of the Invention
The present invention relates to an image forming device, and more particularly to an image forming device including a rotary developing device having a plurality of developing units and a rotary frame that maintains the developing units in a circumferential direction in order to place each of the developing units opposite the image bearing member by means of rotation.
2. Background Information
An image forming device utilizing an electrophotographic system includes a photosensitive drum as an image bearing member and other devices located circumferentially around the drum, such as a charger, an exposure device, a developing device, a transfer device, a cleaning device, and so on. In addition, a fixing device is provided downstream of the photosensitive drum in a direction in which the transfer media are conveyed. In this image forming device, first, a surface of the photosensitive drum is uniformly charged by the charger. Then, the photosensitive drum is exposed by the exposure device in accordance with image data so that an electrostatic latent image is formed on the photosensitive drum. The electrostatic latent image is developed by the developing device. In the case of a full color image forming device, four developing units are provided for storing cyan developer, magenta developer, yellow developer, and black developer. The developing units develop the latent image to a toner image with four colors (cyan, magenta, yellow, and black). After that, the toner image is transferred to a transfer medium by the transfer device and then fixed to the transfer media by the fixing device, and the transfer media is finally discharged to a discharge unit. Residual developer remaining on the photosensitive drum is cleaned by the cleaning device.
In the above-mentioned image forming operation, the toner in the toner container is consumed as the development is carried out, and thus it is necessary to refill the toner. There are two systems to compensate for the toner consumed by the image forming operation.
The first system is to fill a certain amount of the toner in the developing unit and replace the developing units when the toner is completely consumed, as shown in Japanese Unexamined Patent Publication No. 2004-45960. In this system, the developing unit and the toner container are formed into a cartridge, so that it is not necessary to supply the toner to the developing unit. Consequently, it is easy to maintain the developing unit.
The second system is to provide a toner container outside of the developing unit so as to supply the toner to the developing unit from the outside, as shown in Japanese Unexamined Patent Publication Nos. 2001-134045 and 10-198149. Recently, as full color image forming devices have been increasingly used by individuals, there have been demands to reduce the size of the image forming device. It is necessary to reduce the size of the developing units in order to reduce the size of the image forming device. In the second system, by providing the toner container outside of the developing unit, the developing unit will be reduced in size.
In the device shown in Japanese Unexamined Patent Publication No. 2004-45960 in which the developing unit and the toner container are formed into a cartridge, it is necessary to place enough toner for about 4,000 sheets of printing in the developing unit in advance, because the toner is not supplied to the developing unit from the outside. As a result, it is difficult to reduce the developing unit in size. Although it is possible to set a toner printing capability to 4,000 sheets or less in order to reduce the size of the developing unit, in that case the cost per one sheet increases. In addition, when the toner is completely consumed, it is necessary to replace the developing units each time. As a result, it increases the burden on the environment.
On the contrary, in a system in which the toner container is provided outside of the developing unit and the toner is supplied to the developing unit from the outside, it is necessary to prepare a member for supplying the toner from the toner container to the developing unit. For example, a plurality of toner supply paths are provided for supplying the toner to each of the developing units in the device shown in Japanese Unexamined Patent Publication No. 2001-134045, and a plurality of toner supply pipes are provided for supplying the toner to each of the developing units in the device shown in Japanese Unexamined Patent Publication No. 10-198149. The toner is supplied to the developing units through the toner supply paths or the toner supply pipes from the toner container.
In a rotary developing device having a plurality of developing units and a rotary frame holding the developing units in a circumferential direction in order to place each of the developing units opposite the image bearing member by means of rotation, it is necessary to advance the toner supply pipe into the developing device in order to supply the toner, and pull the toner supply pipe out from the developing device after the toner supply is finished. Furthermore, in order to stop rotation of the rotary frame when the toner supply pipe is inserted into and pulled out from the developing device, a lock mechanism is provided. The lock mechanism is typically adapted to prohibit rotations both clockwise and counterclockwise. As a result, the lock mechanism generally has a difficult structure.
It is an object of the present invention to provide a simple lock mechanism for locking the position of the developing units during the toner supplying operation in the device which includes a toner container apart from the developing device and a toner supply member for supplying the toner to the developing units.